Negotiators say "substantial progress" has been made after two days of trade talks between China and the United States. They discussed agriculture, intellectual property and expanding trade and technology transfers. Chinese President Xi Jinping said a healthy and steady relationship is good for both countries and the world. And U.S. President Donald Trump gave "tremendous credit" to China for the progress in talks. The two sides also agreed to work towards a final agreement. He Weiwen, a senior researcher from the Center for China and Globalization, has sat down with CGTN and shared his views on what makes of the "substantial progress" and what will be the most difficult part of future negotiations.